The Transportation Security Administration has specific policies on bringing liquids on board airliners in carry-on baggage because of threats to blow up planes using liquid explosives. TSA limits the size and number of bottles passengers can bring aboard in carry-on luggage but sets no limits on bottles in checked luggage. A full list of allowable and non-allowable items is available on the TSA website.
Liquids and other toiletry items must be in containers that hold 3.4 ounces or less per bottle. While there is no restriction on using refillable bottles or jars, they must conform to the TSA’s liquid weight standard. All the containers must fit in a single transparent, quart-sized ziptop plastic bag, so using the smallest container possible allows you to fit more in the bag.
Medications and health-related items such as IV bags are exempt from the 3.4-ounce rule and plastic bag requirement. Liquid-filled containers meant for infants, such as bottles of formula or breast milk, are also exempt from these rules. However, even exempt liquids will be examined by security agents by hand and possibly sent through the X-ray machine. You must notify a TSA agent before the inspection begins that you are carrying exempt liquids and if you don't want the container opened.